Locking of Dislocations without the Application of an External Stress: Experiment and Theory

Abstract

Results of investigation of self-locking effect representing transformation of glide dislocations into the locked ones in the absence of external stress are presented. The effect was predicted theoretically on basis of a simple model considering superdislocation as a pileup, where one of the dislocations contributes to the locking of the other one, and, as a result, both are locked. The proof of the effect occurrence, namely, observation that dislocations elongate along prevailing direction, was experimentally revealed, including a plastic deformation and a subsequent heating without a load. To explain the set of experimental results, a new conception is developed: an effective force, being proportional to the difference of the depths of the valleys, appears, if dislocation has a two-valley potential relief. This force causes transformation of dislocations into an indestructible barrier. Consequently, two effects (the temperature anomaly of the yield stress and the self-locking of dislocations) are of the same common nature. Both effects were observed in the intermetallic compounds such as Ni3Al and TiAl as well as in the pure metals such as Mg.

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